Cancer pain is just a serious symptom, and its basic treatment principle should be to treat both the symptoms and the root cause, that is, treating cancer pain as the symptom and treating cancer as the root cause, and treating the symptom provides the best condition for treating the root cause, and the two complement each other to achieve better treatment effect. Among the various means of cancer pain treatment, drug therapy is the most basic, effective and commonly used method. Especially early and mild cancer pain patients should be treated with drug therapy. Because drug therapy has the advantages of being effective, fast-acting, small risk and reasonable cost. The basic principle is to develop individual treatment plan according to each case. Before choosing medication to treat pain symptoms or other symptoms, it is important to determine the specific cause of pain, assess the intensity and nature of pain, and then choose the medication. Pain relief should begin with the simplest dosing regimen and non-invasive treatments, and the effects of treatment should be closely monitored. There are three major categories of drugs for cancer pain treatment: (1) non-autogenous anti-inflammatory analgesics, i.e. general analgesics; (2) opioid analgesics; (3) adjuvant analgesics, sedatives and neurotropics, etc. Mild cancer pain is generally tolerable and can lead a normal life and sleep basically without disturbance, and should be treated according to the first step. In principle, the first-stage treatment is oral non-autogenous anti-inflammatory analgesics, which act on the terminal and have antipyretic and anti-inflammatory effects, inhibit the production of hypothalamic prostaglandin synthetase and reduce the synthesis and release of prostaglandin E. It is very effective for the pain of patients with high prostaglandin content of bone metastases. The representative drugs are aspirin, paracetamol and fotarol. The starting dose of aspirin is 250-500 mg/dose, and the maximum dose is 1000 mg/dose, which can be re-taken every 4-6 hours to achieve pain relief. Paracetamol is given orally at 0.3- 0.6 g/d once, 0.6- 1.8 g/d, and the course of treatment should not easily exceed 10 d. Fotarolimus is given orally at 25 mg 3 times daily or suppositories at 50 mg/d twice daily. The type of drugs should be changed frequently in the treatment, such as eusanalgesia, ibuprofen, fenbuterol, etc., to reduce gastrointestinal complications and adverse effects. Moderate cancer pain is often persistent, sleep has been disturbed and appetite has been reduced. Such pain patients need to apply analgesic drugs, but in principle, they should adopt the principle of gradual transition to the second step, that is, while giving non-autogenous anti-inflammatory analgesics, they should give auxiliary analgesics, such as tramadol or weak opioid analgesics, such as codeine and dextropropoxyphene. Valium and hypnotics can be given at night, etc. Painkiller is a new non-autologous powerful analgesic and moderate anti-inflammatory and antipyretic drug, mainly by inhibiting the synthesis of prostaglandins, which can bind to opioid receptors and is non-addictive. The analgesic effect of 30 mg of painkiller is equivalent to 12 mg of morphine, and it is a good drug for moderate cancer pain. Prednisolone (AP-237) has the advantage of fast onset of action and is suitable for patients with moderate cancer pain. Severe or unbearable severe pain, sleep and diet are seriously disturbed, and it is difficult to sleep at night and the pain increases. At this time, general analgesics are basically ineffective, and other analgesics or weak opioid analgesics can no longer play an analgesic role. At present, the more commonly used oral drug is Methocarbamol (i.e. morphine controlled-release tablets), each containing 30 mg of morphine, l-2 tablets each time, once every 12 h orally, and if it cannot be taken orally, it can be given anally. Other potent opioid analgesics include morphine, dihydroetorphine hydrochloride, methadone, pethidine, fentanyl, tert-butylphine, buprenorphine, levomorphine, etc. The analgesic is a morphine-like synthetic drug, which agonizes the k-opioid receptor and antagonizes the U-opioid receptor, with weak respiratory inhibition and little dependence. The simple, effective, recognized and reasonable step therapy designed by the World Health Organization can effectively relieve the pain of 90% of cancer patients, and more than 75% of advanced cancer patients can have their pain relieved. The following 5 principles should be observed when taking medication, namely oral, on time, stepwise, individualized medication/attention to specific details.